Cmpeirce123

Hey I have a 1964 Olds F85. I have no tail lights. They turn on when I turn the blinker on with the key off but they only light up they don’t flash. But when I turn the key on they don’t light up even with the blinker on. I replaced the headlight switch and the brights clicker on the floor. I have a 12v light tester. The light lights up in the socket but on the ground not the positive wire. When light switch is turned on both ground and positive have power running to them? But the bulbs don’t light up.

classicmuscle442

Check for corroded ground connections, turn signals should not turn on lights with key in off position. Most problems with old wiring is in the ground circuit.

Cmpeirce123

Ok will do thanks!

oldcutlass

X2 on checking and cleaning grounds. The tail light circuit has a fuse and is independent of the turn signal, the 1157 lamp has 2 filaments.

joe_padavano

Start by reading the wiring diagram in your factory service manual. That will tell you that the 1157 bulbs used in the tail lights have TWO filaments. The tail light circuit is completely separate from the brake/turn circuit. The only place that they are common is the ground for the bulb. The two filaments are tied together at the shell of the bulb. If the socket ground is bad, this can cause backfeeding and all sorts of unusual behavior.

Having said that, it is extremely unlikely that ALL the grounds on both sides are bad, so try troubleshooting the circuits first. The tail lights don't require the key to be on, so simply turn the lights on and check for voltage at the socket with a test light. If you get voltage, the problem is the bulb or the ground. If you don't trace the wire until you find the problem.

Once the tail lights work, do the same with the turn/brake circuit. The brake lights work without the key, but the turn signals require key-on power. Again, check for voltage at the socket terminal and trace the wire back as necessary to find the problem. This is electrical troubleshooting 101.

Cmpeirce123

Ok thanks. I put new bulbs in. Thats when I was able to get one filaments to light up in each bulb. But, only when turn signal was on. I’ll trace the wires and start cleaning grounds today. This car had been sitting in a barn for the last 15+ years. I haven’t found any chewed wires so hopefully it’s just grounds. Thanks

joe_padavano

You really should start by using a test light to see if you have power on the terminal in the socket for the tail light filament, before you replace anything or chase any wires. And if one filament lights, the grounds are good.

Cmpeirce123

I have used a test light on them. The ground wire has power to it on both lights when lights are turned on. Then when turn signal is activated positive and ground both have power.